Insecticide-impregnated fabric and method of production

ABSTRACT

An insecticide-impregnated fabric that remains sufficiently effective at killing and repelling disease vector insects after repeated washings with detergent and water is described. The fabric is impregnated with an insecticide composition containing an insecticide, a cyclodextrin, and a binding agent. The resulting fabric is useful for providing personal protection against disease-carrying insect vectors, particularly when assembled as a bednet in regions of the world where malaria is prevalent, and will remain effective for a longer period of time before re-impregnation is necessary.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication 60/181,770, filed Feb. 11, 2000.

[0002] This invention was made at the Centers for Disease Control andPrevention. Therefore, the United States Government has certain rightsin this invention.

FIELD OF THE INVENTION

[0003] The present invention relates to a fabric or net that has beenimpregnated or coated with an insecticide and methods of producing thefabric.

BACKGROUND OF THE INVENTION

[0004] Malaria is a major cause of child mortality in much of Africa.The mosquito parasite, Plasmodium falciparum, accounts for greater than25% of childhood mortality outside the neonatal period. In parts ofAfrica, malaria has been ranked first by the World Bank in terms ofdisability-adjusted life-years lost. Drug and insecticide resistance, aswell as insufficiently developed and financed health services, havehampered efforts over the past twenty years lo improve the situation. Asa result, the malaria burden has remained largely unchanged.

[0005] Mortality in young children due to mosquito-borne malaria poses asignificant world health problem. insecticide-treated nets and fabricshave been developed since the 1980s as a promising tool for theprevention of malaria in endemic countries. Potent and safe syntheticpyrethroids, such as, permethrin, deltamethrin, lambda-cyhalothrin,alphamethrin, and cyfluthrin, are presently used to treat bednets andcurtains by simply dipping the fabric into a solution containing theinsecticide and allowing the solution to dry on the fabric. Providedthat the nets or Fabrics are not washed more than once to twice,insecticidal activity is retained for up to twelve months.

[0006] Many studies documenting the efficacy of these nets or fabrics toreduce the number of outbreaks of malaria in endemic areas have beenconducted in several countries. Recently, the World Health Organization(WHO), along with twenty other donor agencies, supported fourlarge-scale trials in Africa to document the impact of treated bednetson child survival. The results indicated that the reduction in childmortality with the use of treated nets ranged from 16-33%. Treated nets,in combination with the use of insect repellents, have been suggested asa primary means of protection for high-risk travelers. Although littleevidence is presently available to document the efficacy of treated netsor fabrics for travelers at high risk, the available evidence is socompelling that specific recommendations are often issued to alltravelers exposed to situations that place them at risk for malaria.

[0007] Bednets treated with insecticides have been effective in thecontrol of malaria in many countries. The treated bednets are aneffective method of vector control in areas endemic for malaria andgreatly enhance personal protection. Although there is some concern thatthe placement of the insecticide-treated fabric in close proximity tothe skin, eyes, or mouth of the person being protected may be harmful,existing toxicology data on pyrethroids indicates that unlike othertypes of insecticides, these chemicals have been shown to be very safe.

[0008] The application of a residual insecticide to fabrics as a meansof personal protection against vector-borne diseases has been attemptedfor some time. During World War II, the impregnation of bednets andcombat fatigues by the Soviet, German, and U.S. armies was first tried.In the late 1970s pyrethroids were used for this purpose; their highinsecticidal activity combined with low mammalian toxicity made themideal for treating fabrics. A scientific panel convened in 1983 by WHOreviewed the first laboratory evidence and recommended the initiation offield trials to assess the potential of this technology for diseasecontrol.

[0009] Unfortunately, currently employed techniques for treating fabricswith insecticides are unable to maintain an effective level of activeingredient at the surface of the net or fabric to kill or repelmosquitoes, especially after repeated washings. In addition, currentlyavailable methods for applying insecticides to fabrics are expensive,which make their use impractical for underdeveloped countries.Furthermore, the available techniques utilize emulsions that varygreatly between manufacturers and do not provide consistent andeffective results.

[0010] Therefore, what is needed is a wash durable insecticide treatednet or fabric wherein the active ingredient is easily incorporated intothe fabric and is prevented from being washed off, thereby maintainingthe insecticide at the fabric surface to permit interaction with targetarthropods for a prolonged period of time, even after repeated washings.

SUMMARY OF THE INVENTION

[0011] An insecticide-impregnated fabric and all insecticide compositionfor impregnating fabric are provided. The impregnated fabric maintains asufficient amount of insecticide on the fabric surface to kill or repelinsects, particularly mosquitoes, even after repeated washings. Thefabric can be made into a net, clothing, and the like, for protectionagainst insect-transmitted diseases such as malaria. Methods forproducing the insecticide-impregnated fabric are also provided. Inaddition, an insecticide composition for treating fabrics is provided.

[0012] The insecticide solution contains a water-soluble cyclodextrin, apolymeric binding agent, and an insecticide. The preferred binding agentis polyvinyl acetate (PVA). The preferred insecticide is a pyrethroid.The cyclodextrin and insecticide in the insecticide solution bindtogether to form an inclusion complex, wherein the insecticide acts as a“guest molecule” nestling in the center of the hydrophobic interior ofthe water-soluble cyclodextrin. The fabric is impregnated by immersingthe fabric in the insecticide solution and allowing the wetted fabric todry. The inclusion complex binds to the fabric and allows theinsecticide to remain attached to the fabric, even after several washeswith a detergent and rinses, thereby prolonging the insecticidaleffectiveness of the fabric.

[0013] Treatment of fabric with the insecticide composition describedherein reduces the rate at which the insecticide is removed from thetreated net during washings. Fabrics treated with the insecticidesolution provide higher insect mortality than fabrics treated usingsolutions that lack the combination of a water-soluble cyclodextrin anda polymeric binding agent. Increased insecticidal effectiveness andwash-durability correlate strongly with the concentrations ofcyclodextrin and binding agent in the solution used to treat the fabric.

[0014] The method provided herein is a simple process that combines theuse of polymer water-compatible emulsions and a water-solublecyclodextrin to attach insecticide to bed nets and other fabrics. Use ofthe method described herein results in a product that is superior overpresently available bednets and provides a more durable and effectiveinsecticide barrier at the surface of the net or fabric. The use of thetreated nets and fabrics provided herein results in more effectivenuisance and/or vector arthropod control, which is associated with areduction in disease transmission.

[0015] The insecticide-impregnated fabric can be used in the manufactureof various end-user items such as, but not limited to netting, clothing,bedding, curtains and tents. Alternatively, fabric and existing fabricproducts can be treated and retreated with the insecticide compositionusing the method described herein. The fabric-impregnating method, usingthe insecticide composition, results in a product that is superior inperformance, simpler to use, and lower in cost than currently availableinsecticide-impregnating or coating methods. Furthermore, the materialsused in the method are less hazardous and more environmentallyacceptable than those currently available.

[0016] It is therefore an object of the present invention to provide aninsecticide-impregnated fabric in which the insecticide has extendedeffectiveness after multiple washings of the impregnated fabric with adetergent.

[0017] It is a further object of the present invention to provide asimple, inexpensive method for impregnating an insecticide into afabric, particularly permethrin formulations.

[0018] It is a further object of the present invention to provide aninexpensive insecticide composition to be used to impregnate a fabricwherein the composition can be easily and quickly applied to the fabric.

[0019] These and other objects, features and advantages of the presentinvention will become apparent after a review of the following detaileddescription of the disclosed embodiment and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a graph showing the effect of wash/rinse cycles onmosquito knock-down after exposure of three strains. of A. gambiae (KIS,diamonds; G3, squares; AB, triangles) to polypropylene bednet samplescoated with permethrin alone (500 mg/m²).

[0021]FIG. 2 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of three strains of A. gambiae (KIS,diamonds; G3, squares; AB, triangles) to polypropylene bednet samplescoated with permethrin alone (500 mg/m²).

[0022]FIG. 3 is a graph showing the effect of wash/rinse cycles onmosquito knock-down after exposure of three strains of A. gambiae (KIS,diamonds; G3, squares; AB, triangles) to polypropylene bednet samplescoated with permethrin alone (1000 mg/m²).

[0023]FIG. 4 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of three strains of A. gambiae (KIS,diamonds; G3, squares; AB, triangles) to polypropylene bednet samplescoated with permethrin alone (1000 mg/m²).

[0024]FIG. 5 is a graph shoving the effect of wash/rinse cycles onmosquito knock-down after exposure of A. gambiae (KIS) to polypropylenebednet samples coated with permethrin (250 mg/m², diamonds; 500 mg/m²,squares; 1000 mg/m², triangles) in combination with PVA (300, 600, and1200 mg/m², respectively) and cyclodextrin (1250, 2500, and 5000 mg/m²,respectively).

[0025]FIG. 6 is a graph showing the effect of wash/rinse cycles onmosquito knock-down after exposure of A. gambiae (G3) to polypropylenebednet samples coated with permethrin (250 mg/m², diamonds; 500 mg/m²,squares; 1000 mg/m², triangles) in combination with PVA (300, 600, and1200 mg/², respectively) and cyclodextrin (1250, 2500, and 5000 mg/m²,respectively).

[0026]FIG. 7 is a graph showing the effect of wash/rinse cycles onmosquito knock-down after exposure of A. gambiae (AB) to polypropylenebednet samples coated with permethrin (250 mg/m², diamonds; 500 mg/m²,squares; 1000 mg/m², triangles) in combination with PVA (300, 600, and1200 mg/m², respectively) and cyclodextrin (1250, 2500, and 5000 mg/m²,respectively).

[0027]FIG. 8 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of A. gambiae (KIS) to polypropylenebednet samples coated with permethrin (250 mg/m², diamonds; 500 mg/m²,squares; 1000 mg/m², triangles) in combination with PVA (300, 600, and1200 mg/m², respectively) and cyclodextrin (1250, 2500, and 5000 mg/m²,respectively).

[0028]FIG. 9 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of A. gambiae (G3) to polypropylenebednet samples coated with permethrin (250 mg/m², diamonds; 500 mg/m²,squares; 1000 mg/m², triangles) in combination with PVA (300, 600, and1200 mg/m², respectively) and cyclodextrin (1250, 2500, and 5000 mg/m²,respectively).

[0029]FIG. 10 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of A. gambiae (AB) to polypropylenebednet samples coated with permethrin (250 mg/m², diamonds; 500 mg/m²,squares; 1000 mg/m², triangles) in combination with PVA (300, 600, and1200 mg/m², respectively) and cyclodextrin (1250, 2500, and 5000 mg/m²,respectively).

[0030]FIG. 11 is a graph showing the effect of wash/rinse cycles onmosquito knock-down after exposure of A. gambiae (G3) to polyesterbednet samples coated with permethrin and PVA at target concentrationsof 3000 mg/m² and varying target concentrations of cyclodextrin of 3000(diamonds), 6000 (squares), and 12000 (triangles) mg/m², respectively.

[0031]FIG. 12 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of A. gambiae (G3) to polyester bednetsamples coated with permethrin and PVA at target concentrations of 3000mg/m² and varying target concentrations of cyclodextrin of 3000(diamonds), 6000 (squares), and 12000 (triangles) mg/m², respectively.

[0032]FIG. 13 is a graph showing the effect of wash/rinse cycles onmosquito knock-down after exposure of A. gambiae (KIS) to polyesterbednet samples coated with permethrin and PVA at target concentrationsof 3000 mg/m² and varying target concentrations of cyclodextrin of 3000(diamonds), 6000 (squares), and 12000 (triangles) mg/m², respectively.

[0033]FIG. 14 is a graph showing the effect of wash/rinse cycles onmosquito mortality after exposure of A. gambiae (KIS) to polyesterbednet samples coated with permethrin and PVA at target concentrationsof 3000 mg/m² and varying target concentrations of cyclodextrin of 3000(diamonds). 6000 (squares), and 12000 (triangles) mg/m², respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0034] An insecticide-impregnated fabric is provided herein. Theimpregnated fabric maintains a sufficient amount of insecticide on thefabric surface to kill or repel disease vector arthropods or insects,particularly mosquitoes, even after repeated washings with detergent andwater. The fabric can be sewn or otherwise constructed into a bednet,tent, clothing or outerwear as well as an outer covering for furnitureand the like, for protection against insect-transmitted diseases such asmalaria.

[0035] An insecticide composition for treating fabrics and methods forproducing insecticide-impregnated fabrics are also provided. Theinsecticide composition is a solution, emulsion or suspension containinga water-soluble cyclodextrin, a commercial polymer emulsion as a bindingagent, and an insecticide in an emulsifiable concentrate. In accordancewith the production method, the fabric is impregnated by immersion inthe insecticide solution and allowed to dry. The preferred binding agentis polyvinyl acetate (PVA). The preferred insecticide is a pyrethroid.The preferred cyclodextrin is a hydroxypropyl cyclodextrin. Thecyclodextrin and insecticide in the insecticide solution bind to eachother to form an inclusion complex, wherein the insecticide acts as a“guest molecule” nestling in the center of the hydrophobic interior ofthe water soluble cyclodextrin. The inclusion complex binds to thefabric and allows the insecticide to remain attached to the fabric, evenafter repeated washes with a detergent, thereby prolonging theinsecticidal effectiveness of the fabric.

Insecticide

[0036] The insecticide used in the insecticide solution/emulsion ispreferably (for reasons of human safety) a member of the pyrethroidfamily of insecticides, which includes, but is not limited to,permethrin, deltamethrin, cyfluthrin, alpha-cypermethrin, etofenprox andlambda-cyhalothrin. This group of insecticides is particularly effectiveagainst malaria-bearing mosquitoes and is relatively safe and non-toxicto humans. This latter characteristic makes these insecticidesespecially desirable for use in fabrics or garments which are to be wornclose to or adjacent to the skin or body.

[0037] Permethrin is a third generation synthetic pyrethroid that hasbeen approved for use by the Environmental Protection Agency (EPA) andthe WHO. It is the constituent of many household and agriculturalinsecticidal formulations and has also been used to impregnate armybattle-dress uniforms in the field. Currently available formulations andmethods of application have allowed only limited use of permethrin dueto the fact that it washes out of treated fabrics within three to fourwashings. The formulation and method of application described hereinovercome this severe disadvantage.

[0038] Deltamethrin is also a synthetic pyrethroid-based insecticide. Itis a unique insecticide among synthetic pyrethroids in that it has amuch longer duration of activity, and its insecticidal activity is muchstronger than other commonly available insecticides. Because of thisproperty, the doses needed for mosquito protection are extremely low,generally in the range of 3 to 18 g, making this insecticide highlyeconomical. Deltamethrin is also advantageous because its activitypersists over a wide range of temperatures. The low toxicity of thischemical makes it particularly desirable for use as part of a coatedgarment that is to be worn next to the skin or in close proximity tofoodstuffs and the like.

[0039] Cypermethrin is yet another synthetic pyrethroid that, along withits emulsifiable concentrate formulations, are non-phytotoxic and have avery low order of dermal toxicity. It is considered to be among theleast toxic of the synthetic pyrethroid insecticides. Alpha-cypermethrinis a racemic derivative of cypermethrin that is much more active forinsecticidal activity than its parent compound.

[0040] As one skilled in the art would appreciate, the formulation ofthe current invention is not limited to the above-mentioned pyrethroids.Newer synthetic pyrethroids such as cyfluthrin and lambda-cyhalothrinalso can be used. Additionally, as one skilled in the art wouldappreciate, any insecticide which is safe for humans and has the desiredlevel of effectiveness against pests may be used.

Cyclodextrin

[0041] The cyclodextrin in the insecticide solution is a non-reducingcyclic oligosaccharide having at least six anhydroglucose units linkedin a ring by α-1.4. bonds. Cyclodextrins are produced by the action ofthe enzyme cyclodextrin glucosyltransferase on starch. The most commoncyclodextrins arc α-, β-, and γ-cyclodextrins having six (α-), seven(β-), or eight (γ-) anhydroglucose units in the ring structure.Therefore, the preferred cyclodextrins for use in the insecticidesolution described herein are α-cyclodextrin, β-cyclodextrin andγ-cyclodextrin or combinations thereof. Because of its high degree ofwater solubility, which is important to the ease of preparation and theeffectiveness of the final product, a hydroxypropyl cyclodextrin is morepreferred. The most preferred cyclodextrin is hydroxypropylβ-cyclodextrin. All the hydroxyl groups in cyclodextrins are oriented tothe outside of the ring while the glucosidic oxygen and two rings of thenon-exchangeable hydrogen atoms are directed towards the interior of thecavity. This combination gives cyclodextrins a hydrophobic inner cavityand a hydrophilic exterior. The insecticide of the insecticide solutionacts as a “guest molecule,” nestling in the center of the hydrophobicinterior, thus forming inclusion complexes. These inclusion complexesbind to the fabric and allow the insecticide to remain attached to thefabric through several wash/rinse cycles, thus prolonging theinsecticidal effectiveness of the fabric or material.

Polymeric Binding Agent

[0042] The preferred polymeric binding agent of the insecticide solutionis polyvinyl acetate (PVA). The primary function of the binding agent isto enhance the binding of the cyclodextrin/insecticide inclusion complexto the fabric. The selection of PVA as the preferred binding agentprolongs the insecticidal performance of the fabric, particularly whenused as a bed net. Nets produced using the insecticide solutioncontaining PVA remain effective much longer than nets produced usingother polymeric emulsions. Thus, PVA was believed to be an optimalsubstance for use as binder, resulting in a more effective and longerlasting surface level of insecticide.

Impregnation Method

[0043] The insecticide solution or emulsion described above is appliedto the fabric using methods well known to those skilled in the art, suchas, but not limited to, dipping the fabric into the solution one or moretimes, soaking the fabric in the solution for a specific amount of time,or spraying the solution onto the fabric. One skilled in the art couldeasily appreciate that the dipping or soaking can occur in a variety ofcontainers or receptacles for a sufficient amount of time to impartinsecticidal properties to the fabric. Furthermore, the formulation ofthe insecticide solution can be used with a variety of aerosol sprayingtechniques as well as non-aerosol spraying techniques. Such sprayingdevices may include, but are not limited to, hand held sprayer andsprayer bottles as well as industrial size applicators.

Fabric

[0044] The fabric to be impregnated with the insecticide of theinsecticide solution described above includes a variety of differentfabric and fabric-type materials and can include natural as well assynthetic fibers or threads. In a preferred embodiment, the fabric is aloosely-woven netting material. This type of fabric is particularlyuseful as a bednet, which is a net arranged in a loose tent-likeconfiguration, most preferably over a sleeping person, to prevent insectbites during the night. The preferred netting is composed of a varietyof materials including, but not limited to, polyester, polypropylene,and polyester or polypropylene derivatives. The fabric can also be wovenor sewn into a variety of different materials, including an article ofclothing and a tent for outdoor covering such as a tarp or enclosure.The article of clothing can also include military battle dress clothingand material. The fabric can be also woven into a material that isdisposable. Furthermore, the fabric can be adapted to form the outercovering of furniture or the like.

[0045] One particularly preferred embodiment of theinsecticide-impregnated fabric that is particularly useful in an areawhere mosquito infestation is endemic is outer clothing made of bednettype material that can be worn over conventional clothing. This outerclothing would provide protection from mosquitoes during the day forpersons engaged in activities such as walking, hiking, farming and thelike.

[0046] It should also be appreciated that the fabric can be constructedinto a hood or hat material to cover the head, neck and face area. Thistype of fabric is useful for protecting these highly vulnerable areas ofthe body.

[0047] The present invention is further illustrated by the followingnon-limiting examples, which are not to be construed in any way asimposing limitations upon the scope thereof. On the contrary, it is tobe clearly understood that resort may be had to various otherembodiments, modifications. and equivalents thereof which, after readingthe description herein, may suggest themselves to those skilled in theart without departing from the spirit of the present invention or thescope of the appended claims.

EXAMPLES Example 1 Preparation of Insecticide Impregnated Bednet Samples

[0048] Insecticide-impregnated bednet samples were prepared as follows.A 3.2 ml volume of de-ionized water and a calculated volume of aparticular insecticide formulation, to achieve a desired targetimpregnation level for the insecticide, was added to a 30 ml beaker.Four 12.5×15.5 cm pieces of polypropylene or polyester netting wereevenly stacked on top of each other, then folded several times. Thestack of folded netting pieces was then placed into the beakercontaining the prepared impregnation solution, and the stack was kneadedabout in the beaker for several minutes. A piece of aluminum foil wasplaced over the beaker to prevent evaporation, and the beaker was placedupside down for at least 1 hour to facilitate further equilibration. Thestack was then removed from the beaker, unfolded, and individual nettingsamples lain flat, in order from top to bottom, on a piece of aluminumfoil for drying. After drying was complete, samples 1 (top) and 4(bottom) were taken and subjected to gas-chromatographic analysis forinsecticide content (see below), and the two values obtained wereaveraged to provide a good approximation of the dosage level of the tworemaining samples of impregnated netting, intended for use in eitherwashing or dose-response (mortality) studies.

[0049] Alternatively, single 12.5×15.5 cm pieces of netting were dippedin an excess volume of treatment solution. Then, the excess solution waswrung Out and the sample placed on aluminum foil for drying. Thedeposited insecticide concentration on the netting sample was thenestimated by knowing the concentration of insecticide in the treatmentsolution and the approximate volume of treatment solution retained afterwringing out.

Bioassays

[0050] Insectary-reared and sugar-fed Anopheles gambiae mosquitoes(Kisumu [KIS], G3 and Asembo [AB] strains), 3-4 days old, were testedfor susceptibility (or resistance) to permethrin-impregnated nets, usingthe WHO adult mosquito susceptibility test kit. About 20 mosquitoes wereused in each assay. Cohort mosquitoes were then used to bioassay thepyrethroid-impregnated netting samples using the WHO cone bioassay witha 3 minute exposure time. During an assay, the cone was held on itsside, which placed the net sample in a perpendicular or verticalposition with respect to the floor, as is the case when testing anactual hanging net. In each assay 7-12 mosquitoes were used with 3-4such assays run for each experiment. After exposure for the prescribedtime, mortality was determined after the mosquitoes were held overnight(24 hours) in clean cartons with sugar water for nourishment. Finalmortality was corrected for control mortality. Knock-down was defined asthe number of mosquitoes alive or dead, present on the floor of thecarton 30 minutes after exposure. Knock-down is considered to be a moreaccurate measurement of insecticide efficacy because in the wild anymosquito that falls to the ground serves almost immediately as food forother insects (e.g., ants). Temperature and humidity conducive to thesurvival of the mosquitoes were maintained.

Gas-Chromatographic Analysis of Insecticide-Impregnated Netting Samples

[0051] The concentration of insecticide impregnated onto the netting wasdetermined as follows. The samples of impregnated netting were placedinto 20 ml scintillation vials, and 100 μl of the appropriate internalstandard solution (IS) was added, followed by 20 ml of acetone. Thesamples were shaken on a mechanical shaker for 30 minutes. For eachsample, 100 μl of the acetone extract was transferred to an auto samplervial followed by 0.9 ml of acetone. After capping, 1 μl of each samplesolution was automatically injected into the gas-chromatographic (GC)system to determine insecticide content. The GC system conditionsincluded a 30 m×530 μm fused silica capillary column (DB-17), 1 μm filmthickness (J & W Scientific. Folsom, Calif.); carrier flow (nitrogen)=12ml/min; column temperature=200° C. for 5 minutes, 30° C./min to 280° C.;detection=electron capture; detector temperature=310° C.; and injectortemperature=270° C.

Washing

[0052] Netting samples were repeatedly washed and each wash and rinsesolution was analyzed to determine the concentration of impregnatedinsecticide removed during each wash cycle. After several wash/rinsecycles, when the insecticidal efficacy had become depleted, the residualinsecticide on the net was also determined.

[0053] A volume of 100 ml of a standardized detergent (2% aqueous sodiumdodecyl sulfate [SDS]) was added to a 4 ounce wide mouth screw-capbottle. An impregnated net sample (bioassayed beforehand) was foldedtwice and placed into the SDS solution, and the cap was applied and thebottle was shaken for 5 minutes on a mechanical shaker. After removingthe cap, the net sample was removed, wrung out and placed in a 4 ouncebottle containing 100 ml of de-ionized water and shaken for fiveminutes, after which, the sample was removed, wrung out and left to dryovernight. The sample was rebioassayed the next day and at later times.To each wash solution was added a volume of 100 μl of the appropriateinternal standard (IS) solution in acetone, and the contents werevigorously shaken by hand. To the rinse solution was added a 0.5 gquantity of dry SDS, and the contents were shaken to dissolve the SDS.Then a 100 μl volume of IS was added, and the contents were vigorouslyshaken. Two ml of each wash and rinse solution was then transferred to a4 ml screw-cap vial, 3 ml of ethyl acetate were added and the contentswere shaken. After centrifugation to clarify the ethyl acetate layer,about 1 ml of the ethyl acetate layer of each extract was transferred toan autosampler vial and injected onto the GC system described above todetermine insecticide content.

[0054] For washing experiments involving permethrin, the wash and rinsesolutions were injected directly onto a reversed-phase, high-performanceliquid chromatographic system with ultraviolet (UV) detection, todetermine the permethrin content of the solutions.

Results

[0055] In bednets treated with permethrin alone, there was a dramaticdecrease in the effectiveness of the bednet within one to fivewash/rinse cycles as measured by knock-down and mortality. Nets treatedwith 500 mg/m² of permethrin alone were completely ineffective againstthe AB strain of mosquitoes after just one wash rinse cycle (FIGS. 1,2). By two wash/rinse cycles, knock-down and mortality had decreased toapproximately 20 and 10%, respectively, for the G3 strain. After fivewash/rinse cycles, there was less than 50% knock-down and onlyapproximately 20% mortality in KIS mosquitoes exposed to nets treatedwith 500 mg/m² of permethrin alone. By six wash/rinse cycles alleffectiveness against all strains had completely disappeared.

[0056] Similarly, nets treated with 1000 mg/m² permethrin alone, lostmost of their effectiveness against all the strains of mosquitoes afterfour washings (FIGS. 3, 4). When bednets were treated with permethrinalone, most (63-90%) of the insecticide was lost after the first washing(Table 1A, B). This makes bednets prepared by treatment with insecticidealone highly impractical and ineffective. TABLE 1 Post Wash/Rinse CycleConcentration Of Permethrin In Bednets Treated With Either 500 Or 1000mg/m² Of Permethrin Alone Amt washed off Amt (%) during a washed off W/Rcycle during a W/R Wash Cycle # mg mg/m² cycle A W/R = 0 — — —  500mg/m² W/R = 1 1.33 68.64 63.0 W/R = 2 0.09 4.65 4.3 W/R = 3 0.10 5.164.7 W/R = 4 0.37 19.10 17.5 W/R = 5 0.16 8.26 7.6 W/R = 6 0.06 3.10 2.8B W/R = 0 — — — 1000 mg/m² W/R = 1 8.43 435.07 90.7 W/R = 2 0.22 11.352.4 W/R = 3 0.08 4.13 0.9 W/R = 4 0.08 4.13 0.9

Example 2 Bednets Treated With Permethrin, Cyclodextrin and PVA

[0057] Wash-durable impregnated bednet samples are prepared as follows.A permethrin net impregnation solution or emulsion or suspension isprepared by adding permethrin, PVA, and cyclodextrin to a quantity ofwater calculated to result in a predetermined permethrin concentrationfor a single dipping cycle. Usually, a weighed quantity of hydroxypropylβ-cyclodextrin (or other appreciably water-soluble cyclodextrin) isfirst dissolved into a volume of water. A specific volume of permethrinemulsifiable concentrate formulation to give the desired impregnationconcentration, is slowly added to the aqueous cyclodextrin solution withstirring. After further stirring for 1-2 hours to allow inclusion of theinsecticide into the cyclodextrin, a commercial PVA emulsion is addedwith stirring, usually at the rate of 1 drop per ml of resultingimpregnation/treatment solution. A 12.5×15.5 cm piece of 100 denier,polyester or polypropylene netting is folded several times and dippedinto the suspension. Excess solution is removed by pressing, the foldednet piece against the sides of the container holding the impregnationsuspension. The netting is unfolded and placed flat upon a piece ofaluminum foil for a few hours to allow drying, thus forming a polymerlayer on the net containing the permethrin/cyclodextrin inclusioncomplex. For a particular experiment, this dipping process may berepeated 1-2 more times.

[0058] Polypropylene bednet samples were prepared as described above atpermethrin target concentrations of 250, 500 or 1000 mg/m² incombination with cyclodextrin (at target concentrations of 1250, 2500 or5000 mg/m², respectively) and PVA (at target concentrations of 300, 600or 1200 mg/m², respectively). The net samples were tested as describedabove in Example 1.

Results

[0059] The polypropylene bednet samples impregnated with the treatmentsolution containing permethrin, cyclodextrin, and PVA, as described,were significantly more effective against all strains of mosquitoes thanbednets treated with permethrin alone. Bednets treated with permethrinin concentrations of 250 to 1000 mg/m² after ten wash/rinse cycles werestill 60 to 100% effective in knock-downs against the KIS strain (FIG.5). Similarly, after ten wash cycles nets treated with the permethrin,cyclodextrin, and PVA formulation maintained almost 80% of theirknock-down effectiveness against the G3 strain (FIG. 6). In the ABstrain of Anopheles, one known for its resistance to permethrin, bednetsmaintained over 60% of their knockdown effectiveness after five washings(FIG. 7). This is in sharp contrast to those treated with permethrinalone (FIGS. 3, 4).

[0060] Bednets treated with the permethrin, cyclodextrin, and PVAformulation also demonstrated significant mortality for a greater numberof wash cycles. Mortality was maintained after ten wash/rinse cycles inthe KIS strain (FIG. 8). Over 60% mortality was maintained in bednetstreated with 1000 mg/m² of permethrin, cyclodextrin, and PVA after eightwash cycles in the G3 strain of mosquitoes (FIG. 9). FIG. 10 shows thateven in the fairly resistant AB strain, over 70% mortality is maintainedafter four wash/rinse cycles. This was significantly greater than inbednets treated with permethrin alone (FIG. 1) in which alleffectiveness with this strain was lost after one wash/rinse cycle.

[0061] The effectiveness of the permethrin, cyclodextrin. and PVAformulation can be further appreciated by the results in Table 2, below,which demonstrate that relatively little permethrin is washed off perwash cycle compared to nets treated with permethrin alone (Table 1).Thus, the formulation allows more insecticide to remain on the netfollowing repeated wash/rinse cycles. The superior results on mortalityand knock-down in bednets treated with the formulation described hereinShow its superiority over methods currently used in fighting diseasecarrying mosquitoes. TABLE 2 Post Wash/Rinse Cycle Concentration OfPermethrin In Bednets Treated With 250,500 Or 1000 mg/m² Of Permethrin,Cyclodextrin and PVA Amt washed off Amt (%) during a washed off W/Rcycle during a W/R Wash Cycle # mg mg/m² cycle A W/R = 0 — — — 250 mg/m²W/R = 1 0.55 28.38 19.4 W/R = 2 0.25 12.90 8.8 W/R = 3 0.31 16.00 10.9W/R = 4 0.18 9.29 6.3 W/R = 5 0.37 19.10 13.0 W/R = 6 0.25 12.89 8.8 W/R= 7 0.19 9.81 6.7 W/R = 8 0.09 4.64 3.2 B W/R = 0 — — — 500 mg/m² W/R =1 0.82 42.32 15.1 W/R = 2 0.39 20.13 7.2 W/R = 3 0.37 19.10 6.8 W/R = 40.24 12.38 4.4 W/R = 5 0.67 34.58 12.3 W/R = 6 0.45 23.22 8.3 W/R = 70.40 20.64 7.4 W/R = 8 0.26 13.42 4.8 W/R = 9 0.18 9.29 3.3 W/R = 100.19 9.81 3.5 C W/R = 0 — — — 1000 mg/m² W/R = 1 1.69 87.22 19.0 W/R = 20.84 43.35 9.5 W/R = 3 0.53 27.35 6.0 W/R = 4 0.67 34.58 7.5 W/R = 50.45 23.22 5.1 W/R = 6 0.37 19.10 4.2 W/R = 7 0.33 17.03 3.7 W/R = 80.45 23.22 5.1 W/R = 9 0.45 23.22 5.1 W/R = 10 0.27 13.94 3.0 W/R = 110.44 22.71 5.0

Example 3 Comparison of Various Concentrations of Cyclodextrin

[0062] Polyester bednet samples were prepared similarly as indicated inExample 2. Treatment solutions/emulsions were prepared to result intarget concentrations of 1000 mg/m² of permethrin, 1000 mg/m² of PVA,and varying target concentrations of concentrations of cyclodextrin of1000, 2000, and 4000 mg/², respectively, following a single dipping.Samples of netting were dipped three times into each treatmentsolution/emulsion, where each sample was allowed to dry overnight beforebeing re-dipped. Thus, the resulting theoretical target concentrations(assuming no material loss of material deposited in previous dippingduring the re-dipping) were 3000 mg/m² for permethrin and PVA and 3000,6000, and 12,000 mg/m², respectively, for cyclodextrin. The net sampleswere tested as indicated in Example 1, above.

Results

[0063] As seen in FIGS. 11-14, increasing concentrations of cyclodextrinincreased the effectiveness of the formulation with respect to bothknock-down and mortality. This increased effectiveness can be seen inboth the G3 (FIGS. 11, 12) and in the KIS strains (FIGS. 13, 14). Thus,with a greater amount of cyclodextrin added to the formulation of thecurrent invention, there was a greater adherence of insecticide to thebednet over a longer period of time. The increased retention ofinsecticide on the bednet can be further seen in Table 3, below, whichshows that there are only very small amounts of insecticide washed offduring each successive wash cycle. TABLE 3 Post Wash/Rinse CycleConcentration Of Permethrin In Bednets Treated With VaryingConcentrations of Cyclodextrin Amt washed off Amt (%) during a washedoff W/R cycle during a W/R Wash Cycle # mg mg/m² cycle A W/R = 0 — — —Cyclodextrin W/R = 1 11.83 611 40.0   3000 W/R = 2 3.07 158 10.3 mg/m²W/R = 3 3.64 188 12.3 W/R = 4 1.24 64 4.2 W/R = 5 1.30 67 4.4 W/R = 61.51 78 5.1 W/R = 7 1.05 54 3.5 W/R = 8 0.88 45 2.9 B W/R = 0 — — —  6000 W/R = 1 15.6 805 42.9 mg/m² W/R = 2 4.07 210 11.2 W/R = 3 2.27327 17.4 W/R = 4 2.94 152 8.1 W/R = 5 1.71 88 4.7 W/R = 6 1.09 56 3.0W/R = 7 1.07 55 2.9 C W/R = 0 — — — 12,000 W/R = 1 7.21 372 21.9 mg/m²W/R = 2 6.67 344 20.2 W/R = 3 2.51 130 7.6 W/R = 4 1.86 96 5.6 W/R = 51.21 62 3.6 W/R = 6 1.53 79 4.6 W/R = 7 0.98 51 3.0

Comparison of Polypropylene and Polyester Netting

[0064] Comparison of the results obtained for Examples 2 and 3 above,indicate that with polypropylene netting. effective, and durable bednetscan be produced using much less (at least five-fold in the case ofpermethrin) insecticide, PVA and cyclodextrin than required forpolyester netting. This is attributed to the mono-filament nature of thepolypropylene “thread” as opposed to multi-filament nature of thepolyester “thread”, providing inaccessible (to the mosquito) areas forinsecticide, PVA and cyclodextrin to bind. Polypropylene is known forits non-adsorptive properties and is not usually recommended for bednetsdue to difficulty in impregnating. Thus, with the use of PVA and acyclodextrin of appreciable water solubility, such as hydroxypropylbeta-cyclodextrin, non-adsorptive materials such as polypropylene can beeffectively treated with insecticides to produce bednets (or otherfabric items for personal protection) of superior quality in terms ofdurability to washing and effectiveness in killing mosquitoes.

[0065] All of the patents, publications and other references mentionedherein are hereby incorporated by reference.

[0066] Modifications and variations of the present methods andcompositions will be obvious to those skilled in the art from theforegoing detailed description. Such modifications and variations areintended to come within the scope of the appended claims.

We claim:
 1. An insecticidal composition for impregnating a fabric withan insecticide comprising an insecticide, a composition which will forman inclusion complex with the insecticide wherein the inclusion complexhas a hydrophobic interior containing the insecticide and a hydrophilicexterior, and a binding agent.
 2. An insecticide composition forimpregnating a fabric with an insecticide comprising an insecticide, acyclodextrin, and a binding agent.
 3. The composition of claim 2 whereinthe insecticide is a pyrethroid.
 4. The composition of claim 3 whereinthe pyrethroid is selected from the group consisting of permethrin,deltamethrin, cyfluthrin, alpha-cypermethrin, etofenprox andlambda-cyhalothrin.
 5. The composition of claim 2 wherein thecyclodextrin is a water-soluble cyclodextrin.
 6. The composition ofclaim 5 wherein the cyclodextrin comprises α-cyclodextrin,β-cyclodextrin, γ-cyclodextrin, and combinations thereof.
 7. Thesolution of claim 6 wherein the cyclodextrin is a hydroxypropylderivative of β-cyclodextrin.
 8. The composition of claim 2 wherein thebinding agent is a polymeric binding agent.
 9. The composition of claim8 wherein the binding agent is polyvinyl acetate.
 10. Aninsecticide-impregnated fabric produced by contacting the fabric with aninsecticide composition comprising an insecticide, a cyclodextrin, and abinding agent.
 11. The insecticide-impregnated fabric of claim 10wherein the composition is a solution, emulsion or suspension and thefabric is dipped into the insecticide composition.
 12. Theinsecticide-impregnated fabric of claim 10 wherein the composition is asolution, emulsion or suspension and the insecticide composition issprayed onto the fabric.
 13. The insecticide-impregnated fabric of claim10 wherein the fabric is a net.
 14. The insecticide-impregnated fabricof claim 13 wherein the net is a polyester net.
 15. Theinsecticide-impregnated fabric of claim 13 wherein the net is apolypropylene net.
 16. The insecticide-impregnated fabric of claim 10having insecticidal properties, wherein the insecticidal properties aremaintained after washing the fabric with a detergent.
 17. A method ofimpregnating fabric with insecticide produced by contacting the fabricwith an insecticide composition comprising an insecticide, acyclodextrin, and a binding agent.
 18. The method of claim 17 whereinthe composition is a solution, emulsion or suspension and the fabric isdipped into the insecticide composition.
 19. The method of claim 17wherein the composition is a solution, emulsion or suspension and theinsecticide composition is sprayed onto the fabric.
 20. The method ofclaim 17 wherein the fabric is a net.
 21. The method of claim 20 whereinthe net is a polyester net.
 22. The method of claim 20 wherein the netis a polypropylene net.
 23. The method of claim 17 wherein the fabrichas insecticidal properties and the insecticidal properties aremaintained after washing the fabric with a detergent.